This invention generally relates to grinding machines known as horizontal grinders, and more particularly to the apparatus and methods that enable access to the grinding drum and for changing the sizing screens.
The grinding of a variety of materials can have a desirable effect. For instance grinding of some types of waste results in increased rate of decomposition, which is useful in landfill operations. Ground wood waste results in mulch, which is useful in landscaping applications. Ground asphalt can be reused. Some types of ground shingles can be used in asphalt production. The benefits of and need for such recycling processes continue to grow.
Several types of machines are useful in the variety of grinding applications. One type is particularly adaptable to a wide variety of applications, known as a horizontal grinder. Horizontal grinders typically include a horizontal feed table onto which the materials to be ground can be placed. The feed table is capable of moving the product to a point where a feed roller begins to cooperate with the feed table, generally pressing down on top of the material and being rotationally powered. The material is then forced, by the cooperation of the feed roller and the feed table, into contact with the side of a grinding drum. The grinding drum is as wide as the feed table and rotationally powered on a generally horizontal axis perpendicular to the direction of travel of the feed table.
The grinding drum typically includes hammers or cutters that impact the material as it is fed from the feed roller/feed table. These hammers or cutters tend to propel the material around the axis of rotation of the drum, eventually moving the material past a stationary bar, typically known as an anvil, that is in relatively close proximity to the outer swing diameter of the hammers or cutters. The material will be reduced in size to some extent, as necessary to travel past the anvil. However, further size reduction is typically required.
The additional size reduction is typically accomplished by the interaction of the hammers or cutters with a sizing screen that is also in relatively close proximity to the outer swing diameter of the hammers or cutters. The sizing screen includes holes to allow the material to pass after being reduced to the desired size. It has been found that the shape and size of the holes affects the performance of the machine and the resulting size of the ground material.
The sizing screens are typically provided on the bottom of the grinding drum, so that as material exits the holes in the sizing screen it will fall to a conveyor. A cover is typically provided over the top of the grinding drum to hold material from being thrown out and to carry material not yet sufficiently ground back around.
The grinding drum, sizing screens and cover are mounted in a mill box that provides the support needed for the tremendous loads that can be generated, particularly when grinding the more difficult materials. These tremendous loads result in the sizing screens being constructed of thick metal, and are thus heavy and difficult to handle. The normal operation of the grinding machine results in substantial loading and wear of the sizing screens. Thus, they must be removed for repair or replacement. In addition, they are changed out to modify the quality of the resulting ground material when being used for varying applications.
In some materials there is a possibility that the material will be wrapped around the grinding drum, between the hammers or cutters, and eventually pinched between the drum and the sizing screens. In this condition there may be sufficient drag on the drum to stall it. In this situation it is necessary to gain access to the drum to remove the wrapped material.